Frank j



Sept. 2 1924. f I 15.901

F. J. CLARK EXPRESSION DEVIQE FOR AUTOIMIG PLAYERS Original Filed Oct. 18. 1919 INVENTOR.

FFH/vf( JT CLHRK Reissued Sept. 2, 1924.

UNITED STATES Re. 15,907 PATENT OFFICE.

BANK CLARK, F MILWAUKEE, WISCONSIN, ASSIGNOR T0 CLARK PNEUMATIC ACTION GODAN'Y, 0F MILWAUKEE, WISCONSIN, A CORPORATION 0F WISCONSIN.

EXPRESSION DEVICE FOR `AUTOMATIC PLAYERS.

riginal No. 1,384,010, dated July 5, 1921, Serial No. 331,589, filed-October 18, 1919. Application for reissue tiled Hatch 6, 1922.

Toall whom zt may concern.'

Be it known that I, FRANK J. CLARK, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and 6 State of Wisconsin, have invented a certain new and useful Improvement in Expression Devices for Automatic Players, of which the following is a full, clear, concise, and exact description, reference being had to the ac- 10 companying drawings, forming a part of this specification. l

This invention relates to expression devices for automatic players.

-Two general methods have been adopted for controlling the expression in pneumatic layer pianos and the like. In each instance, "however, this is accomplished by varying the degree of tension in the playerchest so as to effect a corresponding change in the force with which the hammers are driven against the desired strings. By the first method the degree of tension in the player chest is varied by controllin the communication between the player c est and the source of air tension,'such as the bellows and associated parts. This obviously requires the maintelnance of a maximum tension in the parts connected with the bellows, with the result that the bellows at all times operate under i '30' full load. By the second method the degree of tension in the player chest is varied by the admission of more or less atmospheric air thereto. This method has its advantages over the first method in that the load upon the bellows depends upon the degree of ten- 'sion in the player chest andthe load is consequently reduced with any reduction in the degree of vacuum therein. The first method` has at the present time, however, generally wlsuperseded the second method on account of the sluggish action of the latter due to a heretofore inability to provide a sufficiently sensitive control for the admission of the atmospheric air.

One object of the present invention is the provision of an exceedingly sensitive expression control device Well adapted for, though not limited to, use in systems of the latter -tyref L 'Thei'tension in a vacuum' system of the character referred to is dependent upon the power delivered to the bellows and upon the ener'l required of the system in producing t music. For instance, assuming Serial No. 541,584.

that the power delivered to the bellows is are being played. This tension must, however, be maintained above a definite allowed minimum degree in order to produce proper action of the player parts.

Another object of the invention is therefore to provide means for accom lishing this purpose by automatically contro ling the admission of atmospheric air to the system.

Another object is to provide an exceedingly simple eX ression device for player pianos and the lilie.

Other objects and advantages will hereinafter ap ear.

One em odiment ofthe invention is illustrated in the accompanying drawings.

The views of the drawings are as follows:

Figure l is a longitudinal sectional view ythrough van expression control device, made in accordance with the present invention, and illustrating diagrammatically the manner of connecting the same with a pneumatic system.

Figure 2 is a sectional view of a certain valve mechanism employed.

The embodiment of the invention shown includes a vacuum chamber 10 communicating preferably with a player chest 11 of any standard or 'approved construction by means of a pipe 12. The usual bellows (not shown) communicate with the player chest to el'l'ect a partial vacuum therein and consequently in the vacuum chamber 10 due to the pipe connection 12.

The vacuum chamber is provided with an air inlet preferably constituting a single opening 13 through which atmospheric air may enter the chamber to reduce the vacuum therein, as well as in the player chest, to any desired degree.

A valve mechanism is employed for controlling the passage of air through said opening. In the present instance, this valve mechanism includes a pneumatic 14 in the form of a bellows havin a fixed wall 15 rigidly mounted preferab y on the vacuum chamber. The movable wall 16 is interposed between the fixed wall l5 and the opening 13 and 'carries a valve 17 of any appropriate material, such as leather yor felt, forcover'ing the openin 13 when the vacuum system is at rest. small bleed opening 18 is provided through, the valve and movable wel through which tension 'of the air in the pneumatic is at all times under the influence of the air tension in the chamber. Thus it wil'be seen that when a partial vacuum is set up in the player chest 11 and the vacuum chamber 1() by the kactuation of the main pump or bellows, a correspending reduction in fair pressure is caused in the pneumatic 14, with the resuslt that the pneumatic 14 tends to collapse and thus lift the lvalve 17 away inem 'the opening 13 to permit :air to enter the chamber. The greater the tension in the chamber 10, the further the valve 17 will 'be moved :from closing position.

Means is provided .for limiting or oontrolling this opening or lifsting movement of vthe vailve so diat very fine adjustments of the vazlve movementsl .many be fhad. For this purpose, the movable wall 16 is puovided with-an extended anni 19, pneerably of resilient snatenial, although a rigid arm might be employed. Vfhen the pneumatic system is at rest, this larm assumes fthe full line of Figure 1 in which it projects across the several fixed stops 20, 2l and 22; As soon Yas a paruia'lvacuum is created, however, in the chamber 10, the arm is ycanried upwardly away from these stops by the movable waslll 1:6 until. it engages a fixed stop 23. In this osition, suicient air is admitted through; e opening 13 Yto reduoe the tension in the chamber to such a minimum that the softest tones under normal playing conditions are produced. In order to obtain a nicelyV :graduated increase in tone volume, several movable stops 24, and 26 are provided Vfor selective engagement with the arm 19, .preferably at various points in the .length iihereocf. Thus when the stop 24 is thrust against thearm 19 the arm is forced slightly awayffrom the Vfixed stop 23 toward the fixed stop 20 and the movable wall 16 with the valve 17 is con sequently brought closer Ato the opening 13. This effects a reduction in Athe amount off atmospheric air admitted to the chamber 1() with the result that -aslightly greater tension is 1quickly set up in the chamber and the player chest 11. in the same way, the movablestops 25 or 26 Xmay be thrust against the arm 19 to further limit the Vmovement ort .the welll 16 and valve 17 from the opening 13.

When the arm 19 lis .made lolli a resilient material the surnam ement of ythe :movable stopsalongthe lengp .of lieamn at diienent distaznces fmm Ithe wall-|115 isof importance. Since the deflection cxmsed in-.lthe spr-ing vis proportional to 'the effective there'orf thestnp 26 nearest the wahl 16 basa ,greater limiting @4.69ct on ltlaewall than any. off the other :movable stops. Willen a Arigid .arm isemployed, however, thersame eiect .is prf duced by limiting the throw of each of the` movable stops.

Y The loudest tones are produced by moving the valve 17 againstV the opening 13. This may Vbe accomplished by providing an inlet opening 27 in the pneumatic 14 to completely destroy the vacuum therein. This opening is normally covered by a suitable valve 28 'movable toward or from the opening. When valve 28 is moved to open position the vacuum in the pneumatic 14 is destroyed with the result that the pneumatic is expanded and vthe valve 17 is :forced against the opening 13.

Various means may '-be provided for actuating the various movable stops 24, 25 and 26 or the movable valve 28. Such means may be lunder :the Vcontrol of the operator or mounted upon .the movable walls 33, 34 and 35 of .the pneumatics 29, 30 and 31, respectively, Whilevrthe movableixvalve 28is carried by the movable wall 36 of the pneumatic 32. Each of these pneumatics kmay comprise a small bellows of anyV standard* or approved construction which, when in mormal expanded. condition, .retain thewparts in the respective positions shown in the drawings. By exhausting the air from any of the ipneumatics 29, 30 o'r 31 the corresponding stop is actuated .to engage .the arml 19, and .by exhausting the air from the pneumatic 32, the valve 28 is lifted to open position.

Each of .these pneumatics is connected to a valve mechanism 37, which Will now be described, by means of a ypipe 38. This mechanism includes a body lportion having a central chamber 39 .therein which is in constant communieatiionv with the vacuum system throughs pipe 40. The pipe 38-communicates with, a. small chamber 4l which may be placed in communication withthe chamber 39 thnough a valve .port 42. The chamber 41 is .provided With .a second valve port 43 normally open to atmospheric .pressure So that atmosphere is normally admitted to ythe corresponding pneumatic through the llO pipe 38. A single valve 44 is adapted to cover either of the ports 42 or 43. This valve is controlled by a diaphragm 45 suspended across a small chamber 46 which is connectedby a .pipe 47 with the usual tracker board 48 over which the sheet music passes. A partial vacuum is normally maintained'in the ipe 47m1doham1ber 46 by means off Ythe sma lhleed opening 49 communicating with the .exhaust chamber 39. j

EachV pipe 47 .communicates with va suitable opening 50 in the Ltraclier board 48 over which an opening or line of openings in the music sheet may pass. When this occurs air is admitted to the pipe 47 and the diaphragm chamber 46 to lift the diaphragm `l and move the valve 44 to open the port 42 and'close the port 43. This places 'the pipe 38 in communication with the exhaust pipe 40 to Withdraw the air from the selected pneumatic 29, 30, 31 or 32. This eects the f collapse of the selected pneumatic and the pneumatic, return to their normal condition.

The mechanism for maintaining a minimum workin tension in the pneumatic system will now e described. This mechanism may assume various forms but in the present Lil instance includes a pneumatic 51 preferably mounted upon and communicating with the vacuum chamber 10 through a pipe 52, so that the air tension in the pneumatic correspends with the tension in the pneumatic drawings.

Vsionin the system. The movable wall 53 of the pneumatic carries a stop 54 for engaging the arm 19 under certain conditions. A spring 55 yieldably maintains the pneumatic in an expanded condition when the system is at rest with the sto in the position shown in the soon as a partial vacuum is established in the vacuum chamber the pneumatic tends to collapse and thus withdraws the stop 54 away from the arm. The tension of the spring 55 is such that when the tenstem approaches an operative minimum,` t e stop 54 is advanced `inta engagement with the arm 19 to ell'ect a movementof the valve 17 toward the openin 13. The amount of atmospheric air admitted to the chamber 10 is thus reduced and the proper working tension accordingly maintained. v

lIn order .to (guide one in ell'ecting or correcting the a justments of the system, a pointer such as shown at 56 may be mounted upon the movable wall 53 of the pneumatic 51. This 4pointer cooperating with a suitable lfixed scale 57 will indicate at all times the.true tension in the system.

` Various changes may be made in the embodiment of the invention hereinabove specically described without departing from or .sacrifcin any of the advantages of the vinvention ened in the following claims.

I claim:

1. An expression device for pneumatic players including a vacuum system having anair inlet, a valve mechanism for controlling the admission of air through said inlet and. influenced by the tension in said system toward open position, and stops for selectively limitin the opening movement of said valve mec anism to any desired degree to vary the tension in said system.

2. An expression device for pneumatic players including a vacuum system having an air inlet, an outwardly opening valve cooperating with said inlet to control the admission of atmospheric air to said system, means actuated by the air tension in said lsystem for eiiecting an opening movement between said valve and inlet, and means for selectively limiting said opening movement to any desired degree to vary the tension in said system.

3. An expression device for pneumatic players including a vacuum system having an' air inlet, a valve mechanism for controlling the admission of air to said system, a pneumatic iniuenced by the tension in said system for actuating said valve mechanism toward open position, and means for selectively limiting the opening movement of said valve-to any desired degree to vary the tension in said system.

4. An expression device for pneumatic players including a vacuum system havin an air inlet, a valve cooperating with said inlet to control the admission of atmospheric air tosaid system, a pneumatic actuated by Athe air tension in said system for moving said valve toward open position, and means v for selectively limiting said opening movement to any desired degree to vary the tension in said system.

5. An expression device for pneumatic players including a vacuum system having an .air inlet, a. valve cooperating with said inlet to control the admission of atmospheric air to said system, a bellows coinmunicating with the air tension in said system for eiecting an opening movement between said valve and said inlet, and means for varying the air tension in said bellows to control the opening movement between said valve and inlet.

6. An expression device for pneumatic players including a vacuum system having an air inlet, a valve cooperating with said inlet to control the admission of atmospheric air to 'said,system, a pneumatic for effecting an opening movement between said valve and said inlet, means for selectively limiting the opening movement of said valve to any desired degree, and means for varying the air tension in said pneumatic to control the opening movement of said valve and inlet.

7. An expression device for pneumatic players including a vacuum system having` an air inlet, a valve cooperating with said inlet to control'the admission of atmospheric and said inlet, :and mealsV for controlli!! the air tension im .said pnemnatic to conteo such opening monemmt.

8. In a `device of; tbenchwracber the combination cina vacuum-.chamber llaving an .air inlet, a,V valve mechanism forV eontnollang the Ladmiion of air ythrough said finlet and influencedby the 'tension m said ,chamber towards open position, steps for selectively limiting the opening movement of .said valve to an'y dedegree te vary the tension in said chamber, and additional means for emolling the operation of said valve mechanism.v

9. In a device of the chamacter A.described the cmnbination of eavacuum. chamber havingzan'air inlet, any outwardlyV openingvel'vley mechanism fer contnolling the admission of air tlmoug-.r said inlet and innencedv lby blev rtansion in seid r toward pen positien, :and means :tor limiting the opening movement oxf said valve mechanism to desired degree `to vary the tension in said' chamber at will.

1i. Ifne,y device of the character Idescribed the combination of a vacuum chamber fluwing an air inlet, .an outvwlwdrly opening valve cooperating with said inlet to control *the admissionof Aatmospheric fair to said chmber, means actuated by the air 'tension 'in said chamber fforeecting anzopening mouement 'between said valve and inlet, and means :for vthe reparation fof: said valve openating means.

l2. In a device of the character described the combination of a vacuum chamber-,hav-

ing an air inlet, a valve cooperating with said inlet to colitnelthe admissiono atmospheric air to said chamber, a pneumatic connected wthlmi'd valve and actuated by the@ air :tension in said Ichamber for effect.

ingm--cpening movmentbetween said valve :mdnsaid inllet, .and means for limiting opening movement of saidvalve kto any `desired degree.

113. I-n a device of the character described the combination of a vacuum chamber .hav-

ing an air inlet, a pnenmatic,a valve actu-V ated bv said pneumatic forfcooperation withsmid inlet, a bleed dnd: tlmough. said vaflve and emnmnnieating with said pneumatic, an

arm carried bg `,pnelmratic and movablewith said valvmandy means for limiting the movement of said' arm. .Y

die,

M., Inn .device of the nhenaeter described the combination aout 'a vacuum er having anair inlet, a pneumatic, fa valve antalateel hy Saidpuenmate ffm' .cooperation with said inlet, a :bleed duct through said wlw and communicating with ypnemmatie, andimeans-or-,cmitm'lling the air tension in sacid'pneumtic.

11511@ a device of. the character descnibnd the combination off a vaenum'chamber hash,

' ing un ain inlet, a pneumatic, .a waive wenn pil-eric air ftosaidnchamiber, at .leaataonestopi Y fm* limiting the opening movement cfsaid' valve mechanism, and'. a pneumatic for mov.- ing seid. stop.

17. in :a device of thechamcterdesciibed:

the .combination of a vacuum system, valve mechanism :for :admitting atmesphenie am" tev said system .to vary the tension: inV said system, and pneumatic means controlled vby tice air tension in-:said systemY below .acertain degree rior limiting the :opening of said valve mechanism.

18. Ina .device of `the character described the combination ci -a vacuum system having an wir inlet, valve mechanism actuated by the air tension =in said system to admit atmcsphenic air te seidsystem, means for limf iting the opening movement ruf. saiidl `/vuillive mechanism to any -desined degree, and-edf diticnal pneumatic meenswccntrc'l'led by air tension in said system` fforfcontrelling said valve mechanism.

19. 'Im a device cfltihe character `described the combination of a vacuum system lhawfing an inlet, valve mechanism actuated.' by the air tension -infsaid system to admitv ait.- moaplienic -fair to yseid system, -meansor 'liar iting .the opening movement .of fsaid valve meehanismto any desired degree, additional means cantrollediibv the air tension insa/id system for comrmllling .-smidf valve mechanism, .mndimlieuting memelaematedbv said lastwmmed measns for indxiea'tingfthedegreel of. air tension in said system.

20. ilinra device olf the character described' the eomhinationef a vacuumsystem matie in; yconstant communication :with yen anid svetem. and influenced: by the tension xenein. rte ractualize said' vailvewwarvl .0pm position, and means Vfor :controlling the .opening movement of said valve to any desired degree.

21. In a device ofthe character described the combination of a vacuum system having an air inlet, a valve for controlling the admission of air through said inlet, a pneumatic in continuous but variable communication with said system and influenced by the air tension therein to actuate said valve toward open position, and means for controlling the opening movement of said valve. 22. In a device of the character described the combination of a vacuum system having an air inlet, a valve for controlling the admission of air through said inlet, a pneumatic for actuating said valve and having a bleed opening through which a variable communication is established with the air tension in said system, and means for controlling the movement of said valve.

l Y23. In' a 'device of the character desc ribed the combination of a vacuum chamb er havingan air inlet, a valve for controlling the admission of air through said inlet, a pneumatic in constant communication 4with said chamber for actuating said valve toward open position, and an adjustable stop for limiting the opening movement of said valve.

24. In `a device of the character described the combination of a vacuum chamber havin an air inlet, a pneumatic arranged ad] acent said inlet and having means for controlling the admission of air through said inlet,` a communication between said pneumatic and chamber to actuate said pneumatic by the air tension in said chamber, and means for controlling said pneumatic tolcontrol the admission of air through said in et. 1

'25. In a device` of the character described the combination of a vacuum sys'- tem, valve mechanism operable to admit atmospheric air to said system to vary the Vtension in said system, means for controlling the opening of said valve to any desired degree to obtain the desired air tension in said system, and pneumatic means controlled by the air tension in said system for limiting the opening of said valve mechanism toi maintain the air tension in said system above a predetermined minimum. 26. An expression device for pneumatic players including a vacuum chamber having an atmospheric air inlet, a single pneumatic having means cooperating with said inlet to control the admission of atmospheric air to said chamber, a communication be- ,tween said `pneumatic and chamber, whereby said pneumatic is actuated in one direction by the air tension in said chamber, and means for'f admitting atmospheric air to said pneumatic, to actuate said pneumaticY in andther direction.

27. An expression device for pneumatic players including a vacuum chamber having an atmospheric air inlet, a single valve cooperating with said inlet to control the admission of atmospheric air to said chamber, a pneumatic influenced by the air tension in said chamber to move said valve to- Ward open position, and means for admitting atmospheric air to said pneumatic to eilect a movement of said valve toward closed position.

28. In a device of the character described, the combination of a vacuum chamber having an atmospheric inlet, and means for controlling the admission of air through said inlet comprising a pneumatic having a chamber infiuenced by the air tension in said first named chamber, a valve associated with said pneumatic andv inlet and influenced by the air tension in said first named chamber to vary the admission of air through said inlet with changes of air tension in said first named chamber, and Vmeans for modifying the air tension in said last named chamber to modify the action of said valve;

29. Ina device of the character described, the combination of aV chamber having anl atmospheric inlet, a pneumatic having a chamber communicating with said first named chamber, a valve associated with said pneumatic and inlet and influenced by the air tension in said first named chamber to vary the admission of air through said inlet with changes of air tension in said first named chamber, and means for modifying the air tension in said last named chamber to modify the action of said valve.

30. The combination with a vacuum chamber having a port and a valve cooperating therewith `to control the flow of air therethrough, of a pneumatic for VAcontrolling the relative positions of said valve and port, said pneumatic having a chamber and communicating passage through which a partial vacuum is induced in said pneumatic chamber from said vacuum chamber and by which said pneumatic is rendered operative to -maintain the degree of vacuum in said vacuum chamber substantially constant, said passage being restricted so that the air tension in said pneumatic chamber may be varied relativeto that in said vacuum chamber, and means for admitting atmospheric air to said pneumatic chamber to thereby counteract the effect of said passage upon the vacuum in said pneumatic chamber to vary the action of said pneumatic and consequently modify the degree of vacuum in said vacuum chamber.

31. The combinationk with a vacuum chamber having a port and a valve cooperating therewith to control the ow of air therethrou h, of a pneumatic' for controlling the re ative positions of said valve and port, said pneumatic having a chamber and communicating passage through which the air in said pneumatic chamber is influenced at alltimes by the vacuum in said vacuum chamber and byj which saidpneumatic is normally operative to' maintain the degree ofvacuum in said pneumatic chamber substantially constant2 and sheet controlled means for admittm atmospheric air to said: pneumatic cham r to counteract the eect of said passage upon the air in said pneumatic chamber to thereby` modiy the action of sa'id pneumatic and consequently modify the degree of vecuumin said vacuuni chamben l* 3Q. An expressionA device for pneumatic players, comprising a `chamber having a a, pneumatic having, a chamber communicating with. said first namedP chamber, a valve associated with said .pneumaticand cooperating .with saidr ort tocontrol the IEow of air therethrou said valve being arrangedQto move contra to such flow of ai=r to incienso the dow-and for modifying the air tension inn saidlast named chamber to vary the actionY of said valve. .y

33.- An expression 'device for pneumatic players, comprising a' pneumatic s stem having. aportya yneumatic.in luenced y the air tension in sai system and having ay movabe wall Cooperating with Said Port for controlling. the iow of air therethrough, said wellbeing movable inf a direction con tra to such Bow to increase vthe' iiovv,` and for modif. Y'ng the air tension in: said pneumetic'to modify the action of. said. movable walk y 34. Agn expression device for pneumatic players,

comprising a pneumatic system swing a portae pneumatic inuenced by the air tension inv-said. system movable wall coo erating with said port for controll-in the dbw ofA air therethrough, said wall tion contra to such dow to increase the How, and means for controlling. the action of said moyens wen.y c

35. An expression device for .pneumatic players including a vacuum system having an air passage, a valve mechanism actuated by fthe air tension in. said system yfor controlling the dow of air through saidA pas sege,a reslfient'arm movable with said valve mechanism, and a plurality of stops tively operable-u on seid arm. to .resist the movement of valve Aismv 3%. An expression. device for pneumatic players a vacuum system havin en air passage, e valvemechanism actuated by the air tension in said system for controlling the iow of air through said pa e, resilient means movable with said. va ve mechanism, and a plurality of stops selectively operable uponY said resilient means to resist the movement of sald -velvevmecha- DIHIL having a 1 arranged to move 'm a direc-V mee? 37. An expression device for. pneumatic players including a vacuum system having n nair passage, a valve' for controlling the ovv of air through said passage', a pneu maticv actuatedby the air tension in said system for movingsaid vaf'lve in a direction contrato the owef air through sai-id passage, a, spring movable with said' valvefand an adustable stop for resisting the vmovement of said spring.

38.- ln an expression device for pneumatic players the combination of a vacuum chamberhaving an air passage,.a valve' cooperslt ing with said passage for controlling` the How of air tlrerethrough, af single pneumatic fordetermining the position of said valve, said pneumatic being influenced by the air tension in said chamber to move valve contra vto the flow of. through-Jsa-id passage asy the.` air tension in said chamber` im creases. andl means for modifying the action of sus pneumaiem the sesame: said valvel and consequently the air tension inlsaid: chamber. y i

39. The combinationiwitha vacuum chamber: o means including a pneumaticy for varying and controlling the degree of vaeuumin said chamber, a restricted Ypassage constantly open to said chamber and pieumatic through whichfa. artialvaouum is normal induced in sai pneumatic. and; by `whic seid Apneumatic is rendered. operative to maintain the d ree of vacuum rinseid chamber substantie ly constants, fand means for varying thel-e'ectof the vacuum in'mid chamberu chamber.4

40. The combination with a vacuum chember of means including a,v neumatic Yfor varying and` controlling t degree of vacuumin mid chambemarestrictedpaseege opento said chamber through Ywhich-a pertialjveeuum variable with respect .to thetin said chamber is inducedin seid pneumatic and by which said pneumatic lis rendered operativel to maintainrthe degree of vacuum in, said-chamber vsubsltantially constant, and separate sheet controlled meansior varying the degreee vacuum in seid. pneumatic to modify the actionthereof thereby vary the d ree of vacuum in seid chamber. A c

41. device ier varying andcontrolling the vacuum in tlieilayer chest .o agpneu' matic player, said vice including l. matic, a restricted opening in communication with said `pneunuuzic through which a partial vacuum is induced inr ksaid. pneumatic and by' which seid pneumatic ie rendered responsive to iuctuatxons inthe vacuum rin thechest to -maintainsuch vacuum tially constant, fand sheet controlled means including a passage for admitting #new pon-the vacuum im to modify-the action; of said pneumatic and consequently the degree of vacuum in said pheric air to said pneumatic to counteract the effect of said restricted opening upon the vacuum therein.

42. A device for varying and controlling the vacuum in a player chest of a pneumatic player, said device including a pneumatic, a restricted opening in constant communication with said pneumatic throu h which a partial vacuum is induced in sait? and by which said pneumatic is rendered responsive to fluctuations in the vacuum in the chest to maintain such vacuum substantially constant, a second opening for admitting atmospheric air to said pneumatic, and sheet controlled means for controlling the admission of air through said last named opening to vary the action of said pneumatic and consequently the vacuum in said chest.

90 43. In a device for varying and controlpneumatic ling the air tension in a vacuum chamber, the combination of means includin a pneumatic normally operative to maintain the air` tension in the chamber substantially constant, said pneumatic having a chamber and a passage communicating therewith through which a partial vacuum 1s normally induced in said pneumatic chamber from the vacuum chamber, said passage being suiciently restricted to permit variations in air tension in said pneumatic chamber relative to that in the vacuum chamber, and means for varying the air tension in said pneumatic chamber Without varyi the operating capacity of said passage tolilereby modify the action of said pneumatic and consequently the air tension in the vacuum chamber.

In witness whereof, I hereunto subscribe my name this 6th da of Februar 1922.

lzRANK J. LARK. 

